Traditionally the major U.S. stock exchanges (NYSE and NASDAQ) are open for business from 9:30 a.m. to 4:00 p.m.. The rise of electronic communications networks has greatly increased the ability of the individual investor to trade outside of traditional business hours.
A trading session is one business day in a financial market from opening bell to closing bell. All orders are placed during the trading session.
NASDAQ lists its offical trading schedule as follows: Pre-Market Trading Hours from 7:00 a.m. to 9:30 a.m. Market Hours from 9:30 a.m. to 4:00 p.m. After-Market Hours from 4:00 p.m. to 8:00 p.m.
The NYSE lists its European market hours as Monday through Friday 9:00 a.m. to 5:30 p.m. CET (Central European Time).
Most major exchanges have reduced trading schedules on holidays. For instance, on December 24, 2009, the NYSE trading floor will close at 1:00 p.m.
Traditionally used by large and high-net-worth investors, after-hours trading offers the individual investor the opportunity to invest beyond traditional exchange hours. According to the SEC, “Before you decide to trade after-hours, you need to educate yourself about the differences between regular and extended trading hours, especially the risks.”